Fuel filter housing and return valve

Hi all, on top of the fuel filter housing is that the return valve?
ZD30 2000 model non common rail engine.
I am not finding a manual that has this valve there on the housing.

Br. from Iceland
Elmar

Attachment 86412

@nissannewby, can you help this guy?

@mudski, sorry Mark, right up your alley I would think

This is a part for cold climate but i can not find good info on it.
Br.
Elmar
Attachment 86420

I'm guessing it allows warm fuel from the engine to heat the fuel coming from the tank and is probably not used above a certain temp.

Apparently 60c is a good temp for diesel for atomization.

Quote:

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Originally Posted by pollenface

I'm guessing it allows warm fuel from the engine to heat the fuel coming from the tank and is probably not used above a certain temp.

Apparently 60c is a good temp for diesel for atomization.

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From what I have researched, diesel fuel temperature above 48degC starts to lose calorific value by something like 1% per degree, hence why there are fuel coolers on some of the common rail engines to help control this variance. I intend to measure my fuel just out of curiousity, however dont expect to find much info of value to be honest. Good to know what the function is of the device though.

You might be right, I'm just going off some stuff I read on a canadian trucking forum.